Regulatory effect of polyamines and indole on expression of stress adaptation genes in <i> Escherichia coli </i>

Abstract

Background. Indole and polyamines are involved in the regulation of physiological processes in bacteria associated with adaptation to stress, biofilm formation, antibiotic tolerance, and bacterial persistence. However, the molecular targets and mechanisms of action of these metabolites are still poorly understood. In this work, we studied the effect of polyamines and indole on the expression of such genes as: rpoS, relA, and spoT, encoding regulators of the general stress responses and starvation; hns and stpA, encoding global regulators of gene expression; rmf, yqjD, hpf, raiA, rsfS, sra, ettA, encoding ribosome hibernation factors.The aim. To study the regulatory effects of polyamines and indole on the expression of these genes, which are responsible for the adaptation of Escherichia coli to stress.Materials and methods. We used strains of E. coli in this study. The amount of polyamines was studied by thin layer chromatography. The indole concentration was determined by high performance liquid chromatography. Gene expression was studied using real-time RT-PCR.Results. The addition of polyamines putrescine, cadaverine and spermidine to the medium stimulated the expression of all the studied genes. The maximal stimulation was observed at the stationary phase mostly. Putrescine and spermidine had the most significant effect. At 24 h of cultivation, an equimolar conversion of exogenous tryptophan into indole was showed. At this time, the expression of two genes – rmf and raiA – increased.Conclusions. We have shown that polyamines upregulate the expression of all the studied genes at the transcriptional level. The stimulating effect is specific for the phase of the batch culture and the type of polyamine. Indole has a positive effect on the expression of the rmf and raiA genes.

Effects of polyamines and indole on the expression of ribosome hibernation factors in <i>Escherichia coli</i> at the translational level

“…Putrescine, cadaverine, and spermidine hydrochlorides (Sigma) were added to the medium for 2 h of cultivation at the concentrations indicated in the figures. Tryptophan (AppliChem) at 2 mM was added as previously described (Khaova et al, 2022).…”

“…Genes, the expression of which is upregulated by polyamines at the translational level, form the polyamine modulon (Igarashi, Kashiwagi, 2006. At the same time, there are data indicating that the regulatory activity of both polyamines and indole can be displayed on different levels of gene expression (Miller-Fleming et al, 2015;Lang et al, 2021;Khaova et al, 2022). Signaling molecules are able to form the regulatory networks that can form responses to various stresses (Tkachenko, 2012).…”

“…Previously, we studied the influence of polyamines and indole on transcription of the rmf, raiA, sra, ettA, rsfS genes, encoding ribosome hibernation factors, in E. coli (Khaova et al, 2022). These factors are able to reversibly inhibit ribosomes under the conditions of nutrient depletion and other stresses in order to save cell resources and conserve ribosomes for the following rapid restoration of their functioning as soon as normal growth conditions are restored.…”

“…It can be assumed that these signaling molecules are involved in the formation of persistence through modulation of the expression of genes encoding ribosome hibernation factors. This is due to an ability of polyamines to stimulate the transcription of the rmf, raiA, sra, ettA, rsfS genes encoding ribosome hibernation factors, whereas indole is able to increase the transcription of two of them, raiA and rmf (Khaova et al, 2022).…”

The Influence of Polyamines on the Expression of Escherichia Coli Ribosome Hibernation Factor Raia

“…Being induced by indole, RaiA is involved in a persister cell formation [4]. Previously, we showed that, in addition to indole, polyamines are able to stimulate the raiA expression on the transcriptional level [5]. These metabolites have many different effects on cellular processes [6], including those carrying out through the modulation of gene expression [7].…”